Slow Crank, No Start When Warm

By the way with that much drop, I'd start by feeling around the cable connections for "warm." Could even just be a dirty battery clamp at the posts
I would've checked all connections first. I didn't read every post on this matter. If the OP just started having this problem then I rule out the cables being to small as the problem would've been reoccurring. Just from what I have read I'm thinking that possibly the starter is going bad. Also I think that the battery is kinda small, I always run a 1000 cold cranking Amp battery or at least as close as I can get. If all of this always has been discussed I apologize