I started using a granular slow release 6-4-6 store brand from Home Depot in the orange bag. Bad mistake as the granules got stuck in the leaves where they attach to the plant and the leaves burned badly. While that was fine provided i made sure i put the granules down only on the sand/dirt, when i broadcast them one day to speed things up - well, that didn't work well.
Now, don't laugh, plain old miracle grow knock-off formula from Lowe's. I put 2 of the small scoops into a 2 gallon watering can and fertilize every 2 weeks. I use 6 gallons of water and 6 scoops of fertilizer in the bed now. I'm attaching a picture from February to see what the difference is. The ground they're in is just dead sand. I had Gardenias in the bed that were sickly - just nothing going on with them. As i started adding fertilizer around the pineapples the Gardenias bounced back enough for me to transplant them out of the bed that bed as I made the entire area a pineapple patch.
One thing to mention, those twist-offs will sometimes get serrated leaves. Probably 10% of the leaves in the patch will rip you up big time if you're not careful.