I think you have AC problems. Based on your original post, if the outside temp is 97, you can only bring the inside temp down to 85 and that is with running both your AC units. I just don't think that is adequate. If you said those numbers were based on only the 15k unit, then I would believe it, but now with both running. I would have them checked by someone who knows what they are doing before spending big money on replacements.
I have two ACs and I can turn my rig into a meat locker if I want to. I know that shade helps and insulation helps, but I still you have AC problems.