I've been having light brown periods the past 2 months, but they are much lighter for me and not heavier. Plus they start red like when I first leak out(sorry if that sounds nasty) but after light brown. First time was 4 days like a normal period length but honestly how light they were, all 4 days combined would be a normal day for me and I have medium flow, not heavy. I always use regular tampons and usually don't have leaks. The 2nd one though was 1 day but really only about half of one day as I had sex that same night and sex didn't make me bleed. This month I'm late again but I expect when I start(if I start,which I think I will or at least hope) it will be the light brown.
I sometimes get small clots or clumps but the last 2, no clots/clumps.
I know this doesn't answer your question but I will say it's annoying and I know it's not normal, at least for me. I've always been regular but now I'm irregular. I am sexually active too and had sex in April and according to my period tracking app had sex every day of my fertile week. No period in April and then late ones in May, June and now July.
I know it may still be possible for me to be pregnant but I haven't had other symtpoms though(and I know that's possible too).
I go to the doctor soon but not sure what will be said. I haven't took a HPT b/c I just don't feel pregnant really. And my partner doesn't really think I am either.