Hoping someone can give me an idea if this is due to lackluster insulation or if something may be wrong with AC.

The AC system is an American Standard 3-ton 14-seer (i think 80or85btu two stage furnace). The AC was turned on at at 6 or 6:30am and set to 68F so that it would run continuously and it did but at 1PM it was 78F inside and 80F outside. The best i've seen in the difference between outside/inside is about 4 Degrees, although when its on the humidity does seem to go down considerably compared to outside (50% humidity outside).

Yesterday, turned on AC at 5:30AM, at 2:20PM outside was 84F and inside was 80F. I then turned OFF the ACandFan and at 5:30pm it was 90F inside and 88F outside (no ac). I turned on AC at 5:30pm and at 6:30pm it was 87F inside and 86F outside.

So my question is can something be wrong with the AC if after running from about 6AM continuously it was only TWO degrees cooler in the house than outside by 1PM? OR can this all be blamed on not so great insulation in my attic? (I do plan to improve the insulation, thicker layer etc... in the attic and add a gable-Fan for the attic...)
any info appreciated, thanks