I've got strange silver/blue swirls in the emulsion of recently developed FP4+, like Schleiren lines when oil mixes in water. These are NOT drying marks, which I get rarely, but my diffusion enlarger light source prints through nicely. This blue color unfortunately makes an excellent contrast mask, leaving markedly lighter swirls within smooth toned areas in my final prints. Soaking in distilled water, then Permawash and rewashing did not remove these 'swirls'. My development sequence has not changed for years: 1. 1 minute presoak 2. Tray development with Xtol 1+3 3. Acid stop bath 4. Sprint fixer 5. Rinse 5 times in tap water 6. Permawash 7. 20 minute wash in tap water 8. 2 minute soak in distilled water ~200ml + 2 drops of Photoflo 9. Hang diagonal to dry. Any ideas on what caused this and (hopefully) how to remove it? Thanks.