Eric and milehighgirl gave you great advice on when not to order plants. I don't even know of a nursery that will ship blues in the summer. Usually they are shipped in the winter when dormant. It sounds like you received tissue culture plugs. I've had great success with those but as stated above they were received and planted in Jan. I've never waited 6 months to fertilize new plants but I've always used a slow release organic fert. Actually I mix some up in my potting mix and plant it. They have all thrived! The only problems I've run into is N2 defiency from too much wood and or sap wood in my mix. I don't see where the sea weed would cause any harm at all but the iron sulfate may have been applied to hastily. Even so I believe being shipped in the summer is the root cause of your problem.

Thanks Tiffany :) Larry - I did mean to type clusiifolia - too much Google putting words in my head. I wish I could edit OPs after making errors posting late at night. Jeeze. My daughter and I have been calling it the pepperoni clusterf---olia LOL. Yours is a BEAUTY! What kind of light does it get?

IMO, soil is the problem. Lots of sand that seems to be very fine looking at the photo, is impeding drainage. There could be lots of peat in that mix also, and together with sand, it creates problem. It is always recommended to repot newly purchased plant. It allows you to check the root system, pot plant in well draining potting mix, make sure there is no bugs. While sand may be compacting (as fine sand does), peat may have become hydrophobic. When that happens, it repels water. It hardens around roots. So regardless how much you water, it doesn't reach the roots. Hydrophobic peat and fine sand could be compacted creating cement-like mixture. Rather than watering such mix, it is usually much better to replace it. Very simple mix could be made by mixing Cactus & Succulent soil with perlite (or pumice - either one should be sifted to get rid of dust-like particles) in 1:1 ratio. Make sure you get that hardened soil off the roots completely. Shake off what you can, use your fingers to crumble off more, use a chopstick or skewer (or even fork!) to get it off. If some still left on roots, get a bowl of warm water and swish rootball in it. (Warm water helps to soften up hydrophobic peat.) After that, check the roots - get rid of any damaged and set the plant on paper towels to air dry. Prepare pot with drainage holes and new potting mix and pot the plant. If washing the roots, do not water immediately and pot into dry mix. Or let roots dry up bit longer (and callus if you pruned any) and plant could be watered after potting. BTW, rotting roots are obvious: they would be of blackish color, and they are usually soft/slimy. Sand is not recommended in potting mixtures unless it is coarse.

undertheoaksgardener, I really like the idea of watering the hosta with fungicide. I see in the Hosta Library (Pests and Diseases section) that Cleary 3335 is recommended. Unfortunately, being in Canada, many powerful pesticides and fungicides are not available anymore. I travel to the States now and then, I will put fungicide on the list to purchase. Also, we are in lock down. A nearby nursery is only offering curbside pickup. So I can't investigate what products they have available. But I will persevere and purchase a good product later this year. Love the quote by J.C. Raulston! It is so very true! Thanks for the encouragement djacobz and liquidfeet. I am glad that your June and Liberty have made a come back. If I coud get the fungicide, I would apply it to the leaves and roots of plants that I suspect have some rot. Our spring can be very wet and with our clay type soil and tree roots that compact the soil, I get rot on some of my hosta. I know it because plant growth can be terribly slow (and depressing). Years ago I suspected rot on my F. Hyacinthina. I dug it out, cut off the rot and bleached it (Bruce Banyai's method). I separated it into 5 or 6 section. All grew well. But that's a lot of work! So my plan now: try doing a weak bleach soak for the second time. Allow the roots and crown to dry somewhat. I'll plant a few pots----and cross my fingers. I've discovered that I really love large hostas and large potted hostas. I do love smaller hosta---they are so cute! But the large leaved hostas are my ultimate favorite! So it's disappointing to have to separate this hosta into smaller pots. But in this case, it's probably the best thing to do.