Hello

Does anyone know why my java fern would be turning a dark red-ish brown colour (spotted all over the plant). I am new to aquarium plants. I got the java fern a few weeks ago from Petsmart and until the last week I only had a 20W light, but for the last week I have had 65W light (6700K) on in the tank for about 14 hours/day. I don't have any supplemental C02 and I have my hornwort in there from my pond. I can try to post a picture if that might help.

Thanks for anyone who might know! And special thanks to woeisme for his past and future help.