+opk four days earlier than usual! which one !?

Sally
Top to bottom - 18/1 midday, 19/1 midday, 20/1 am, 20/1 pm. I marked the bottom one from late yesterday <a href="https://play.google.com/store/apps/details?id=com.glow.android.eve">eve</a> as positive and glow bought my predicted ovulation forward by four days (I had originally only just come into my fertile window but ewcm prompted extra testing)...
Top to bottom - 18/1 midday, 19/1 midday, 20/1 am, 20/1 pm, 21/1 pm... even darker positive than yesterday evenings !? 
So, thoughts !? Shall I mark this afternoonspositive  instead and just note the one from yesterday!? My cycle usually only varies by two days 28-31days. Af usually arrives ten days after the big O so this would be my shortest cycle yet at only 25 days meaning a variable of up to 7 days for future cycles if we don't catch this month!