Question about dual alt set up 08 f150

[escottl92]

Hello I have a h.o. Alt for my truck and a stand alone h.o. Alt for my cmaxx interior regulator 15.3v,  I have yellow power/ignition wire hooked to a toggle switch

i charged my cmax to 14.4 then hooked power wires on my alt to cmax

i started my truck played a couple songs and it dropped to 14.1v. Could I have fried my internal regulator??

I took wires off that feed cmax and the alt read 13.4 with my charge going out

please advise