Concerta not lasting as long | ADHD Information

DS 10 has been taking concerta 54mg. with a 10mg.ritalin in the am for a
couple of years. Lately we have been getting emails from school saying
that he is not focused and silly after lunch (11-11:50). We just thought it
was his sleep schedule (has been more tired lately even though he gets
about the same amount of sleep). He takes clonidine in the evenings to
get to sleep. He also takes zoloft 50mg for anxiety. We have changed his
diet as best as we can (picky eater) and taken away electronics during the
week. He is just much more emotional these past few weeks and worried.
Things were going so well for so long that I am surprised by this sudden
change. I think we need to try some new meds or do something different.
I just worry that we will run out of options. We have been through most
adhd meds already. Could it just be that he is growing and his body is
changing the way it reacts to the meds? Have your kids gone thru this??