my strongest to lightest is
back
chest
tri
bi
shoulders
i am in meso 2,second week and can still not lift any more in bi and shoulder presses. in p90x i was stronger in both.any suggestions on how to gain strength in those 2 areas?
Actually, until you get to the shoulders, the order of strongest to lightest fits with the size of these muscle groups, so it makes sense (triceps are a larger muscle group than biceps, but because of leverage differences, most people are stronger in biceps than tris).
If you were talking about the delts heads in isolation (anterior, lateral and posterior) rather than the whole deltoid region, I'd say it's not bad, since the three heads are really not that big, but if you're talking about moves like overhead presses, which work all three heads at once, there does seem to be a weakness.
It might be from your body mechanics rather than an actual muscle weakness. Try using dumbells rather than a barbell and using different hand positions to see if they help you push heavier (though you will theoretically be lifting less total weight with the dumbells than with a barbell, they will not allow your weaker side to get off easy by letting the stronger side do more work).
I'd recommend prioritizing the shoulders by doing exercises for them first in your workout (after a warm-up) 1-2 days a week. And be sure to give them enough recovery time.
If you're doing a workout rotation that has you doing chest on day 1, back on day 2 and shoulders on day 3, for example, the shoulders are working all three days.
I personally like to use workouts that have 2 upper-body workout and one lower body workout as follows: day 1: upper-body 1, day 3: lower body, day 3: upper body 2. This gives my shoulders more rest time, which they seem to need both for recovery and for injury prevention.
I also agree that going to your own pace (which was actually what STS was supposed to be about, I'd thought) is a good idea. Some of us (and some of our muscle groups) just need a bit different pace to work the best.
Another suggestion: once a week, you might want to do some assisted negative bicep curls (a concentration curl move is easy to assist on using your other hand). Try a weight that's heavier than usual (for example: if you usually do 12 reps, choose a weight you can do 10 reps with unassisted) then for the last two reps, use your other hand (as little as possible) to help get the weight up, then lower in a controlled fashion without assistance. (Because negative reps cause more muscle damage--which is then repaired--they will also cause more DOMS, so it's best to not do them that often. Like I said, once a week, perhaps).
It's pretty much impossible to do assisted reps for shoulders (unless you have some long prehensile tail that can assist,

) but you could do one-sided shoulder presses, which will usually allow one to lift heavier.
Set yourself up in a very stable standing position, holding onto a support with the non-working hand, then press the weight overhead.
Another way of working shoulders is a (forget what it's called! push press? ) power lifting move: before pushing up the weight, bend your legs a bit, then push up with your legs as you move the weight up with your arms. This will allow you to get a heavier weight up, and also help you get more safely through the 90-degree angle position at the bottom at which the shoulder joint is most vulnerable. (the book "Women's Health Big Book of Exercises" shows this move and some variations on it). Be sure the extra push comes from the legs, NOT the back (don't bend forward at all).
HTH!