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Hello, I ran your site through ahref.com and saw 16 backlinks, when I looked at follow backlinks I saw 10, of those 10 backlinks I see that 8 of those 10 backlinks contain the same anchor text for the same article " The Great History Freeze to preserve photographic negatives: Join The Great History Freeze and help preserve a collection of invaluable and irreplaceable negatives. " This I'd imagine is what is costing you your DA drop, since you basically have 3 follow backlinks, if google is even counting that as legitimate links. You could be suffering a negative SEO issue from those domains using the same text, as well it seems pretty spammy. Now a days google seems to be counting backlinks that are bad less or not at all. I'd imagine that this would be the case and could bet a DA increase would happen if you could acquire even 3 to 5 more backlinks from legit sources. So far, I've seen more correlation between DA and backlinks than I have DA and SEO. I see sites with crap for SEO but a decent backlink profile climb higher and faster in DA than a site with epic SEO and a handful of backlinks or even hundreds of crap backlinks. Quality always matters over quantity.